Thermal turbomachines, such as turbines and compressors, generally comprise a rotor fitted with moving blades and a stator in which the guide blades are suspended.
A task of the fixed guide blades is to direct the flow of the gaseous medium to be compressed or expanded onto the rotating moving blades in such a way that the energy conversion is effected with the best possible efficiency.
Both moving blades and guide blades essentially have an airfoil and a blade root. In order to be able to fasten the moving blades on the rotor or the guide blades in the stator, slots are recessed in the stator and on the rotor shaft. The roots of the blades are pushed into these slots and locked there.
It is known in the case of compressor rotors having circumferential slots to alternately fit moving blades and intermediate pieces in the turned rotor groove (circumferential slot) until an opening remains in the circumferential direction, this opening being filled with a “rotor end piece”. The rotor end piece consists of an intermediate piece divided in half (two end piece halves) and of a wedge. To fit the intermediate piece divided in half, a residual opening is required, which is finally closed by pushing in a wedge. The two end piece halves each have a straight side face, which at its top end forms a projecting lobe with the top surface of the end piece half. Said side faces are opposite one another in the installed state, the wedge then being located between them. Once the two end piece halves and the wedge have been installed, the lobes of the two end piece halves are finally caulked via the wedge. This known rotor end piece is supported on the rotor.
A disadvantage with this prior art is that the wedge, on account of the tilting moment of the two end piece halves, which is caused by the centrifugal forces during operation, is able to bend open the caulked lobes. The wedge can thus fly out of the compressor and complete compressor damage may occur.
Furthermore, the applicant is familiar with a rotor end piece which is intended for rotors of thermal turbomachines having a circumferential slot and consists of two end piece halves having side faces opposite one another in the installed state and top surfaces adjoining one another and in which the side faces of the end piece halves are connected to one another in a form-fitting manner, to be precise by means of a dovetail interlocking connection known per se. In this case, the two end piece halves are locally welded to one another in the region in which the side faces and the top surfaces of the two end piece halves adjoin one another. This is intended to achieve firm anchoring of the rotor end piece in the installed state. Under high stresses, however, this anchoring is often not sufficient.